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Prostate Cancer Chemotherapy

Definition

Prostate cancer is a disease is which the cells of the prostate become abnormal and start to grow uncontrollably, forming tumors. Tumors that can spread to other parts of the body are called malignant tumors or cancers. Tumors that are not capable of spread are said to be benign.

Description

Prostate cancer is the most common cancer among men in the United States, and is the second leading cause of cancer deaths. The American Cancer Society estimates that in 1998, at least 185,000 new cases of prostate cancer will be diagnosed, and it will cause at least 40,000 deaths. Although prostate cancer may be very slow-growing, it is a heterogeneous disease and can be quite aggressive, especially in younger men. When the disease is slow-growing it often may go undetected. Because it may take many years for the cancer to develop, many men with the disease will probably die of other causes rather than from the cancer.

Prostate cancer affects black men twice as often as it does white men, and the mortality rate among African-Americans is also two times higher. African-Americans have the highest rate of prostate cancer in the world.

The prostate, testicles, and seminal vesicles are the major male sex glands. These three glands together secrete the fluid that makes up semen. The prostate is about the size of a walnut and lies just behind the urinary bladder. A tumor in the prostate interferes with proper control of the bladder and normal sexual functioning. Often, the first symptom of prostate cancer to develop is difficulty in urinating. However, because the same symptom can be caused by a very common, non-cancerous condition of the prostate (benign prostatic hyperplasia), it does not always mean that prostate cancer is present.

As the prostate cancer grows, some of the cells break off and spread to other parts of the body through the lymph or the blood. The most common sites to which it spreads are the lymph nodes, the lungs, and various bones around the hips and the pelvic region.

Causes & symptoms

The cause of prostate cancer is not known, however, it is found mainly in men over the age of 55. The average age at diagnosis is 72. In fact, 80% of the prostate cancer cases occur in men over the age of 65. As men grow older, the likelihood of getting prostate cancer increases. While only 1 in 100,000 men will get prostate cancer under the age of 40, the frequency rises to 1,326 cases in 100,000, for men between the ages of 70-74. Hence, age appears to be a risk factor for prostate cancer. Race may be another contributing factor, because African-Americans have the highest rate of prostate cancer in the world.

Some studies have shown that a family history of prostate cancer, puts a man at a higher risk for getting this disease. In addition, there is some evidence to suggest that a diet high in fat increases the risk of prostate cancer. Workers in the electroplating and welding industries who are exposed to the metal cadmium and rubber industry workers appear to have a higher than average risk of getting this disease. Research has indicated that men with high plasma testosterone levels also may be at an increased risk for developing prostate cancer.

Frequently, prostate cancer has no symptoms, and the disease is diagnosed when the patient goes for a routine screening examination. However, occasionally, when the tumor is big or the cancer has spread to the nearby tissues, the following symptoms may be seen:

• Weak or interrupted flow of the urine
• Frequent urination (especially at night)
• Difficulty starting urination
• Inability to urinate
• Pain or burning sensation when urinating
• Blood in the urine
• Persistent pain in lower back, hips, or thighs (bone pain)
• Painful ejaculation.

Diagnosis

Prostate cancer is curable when detected early. However, because the early stages of prostate cancer may not have any symptoms, it often goes undetected until the patient goes for a routine physical examination. Diagnosis of the disease is made using some or all of the following tests.

Digital rectal examination (DRE)

In order to perform this test, the doctor puts a gloved, lubricated finger (digit) into the rectum to feel for any lumps in the prostate. The rectum lies just behind the prostate gland, and a majority of prostate tumors begin in the posterior region of the prostate. If the doctor does detect an abnormality, he or she may order more tests in order to confirm these findings.

Blood tests are used to measure the amounts of certain protein markers, such as prostate-specific antigen (PSA), found circulating in the blood. The cells lining the prostate generally make this protein and a small amount can be detected in the bloodstream. However, prostate cancers produce a lot of this protein, and it can be easily detected in the blood. Hence, when PSA is found in the blood in higher than normal amounts (for the patient's age group), cancer may be present.

A small probe is placed in the rectum, and sound waves are released from the probe. These sound waves bounce off the prostate tissue and an image is created. Since normal prostate tissue and prostate tumors reflect the sound waves differently, the test can be used to detect tumors quite efficiently. Though the insertion of the probe into the rectum may be slightly uncomfortable, the procedure is generally painless and only takes 20 minutes.

If cancer is suspected from the results ofany of the above tests, the doctor will remove a small piece of prostate tissue with a hollow needle. This sample is then checked under the microscope for the presence of cancerous cells. Prostate biopsy is the most definitive diagnostic tool for prostate cancer.

If cancer is detected during the microscopic examination of the prostate tissue, the pathologist will "grade" the tumor. This means that he will score the tumor on a scale of 1 to 10 to indicate how aggressive the tumor is. Tumors with a lower score are less likely to grow and spread than are tumors with higher scores. This method of grading tumors is called the Gleason system. This is different from "staging" of the cancer. When a doctor stages a cancer, he gives it a number that indicates whether it has spread and the extent of spread of the disease. In Stage I, the cancer is localized in the prostate in one area, while in the last stage, Stage IV, the cancer cells have spread to other parts of the body.

X rays and imaging techniques

A chest x ray may be ordered to determine whether the cancer has spread to the lungs. Imaging techniques (such as computed tomography scans and magnetic resonance imaging), where a computer is used to generate a detailed picture of the prostate and areas nearby, may be done to get a clearer view of the internal organs. A bone scan may be used to check whether the cancer has spread to the bone.

Treatment

The doctor and the patient will decide on the treatment mode after considering many factors. For exmaple, the patient's age, the stage of the tumor, his general health, and the presence of any co-existing illnesses have to be considered. In addition, the patient's personal preferences and the risks and benefits of each treatment protocol are also taken into account before any decision is made.

Surgery

For early stage prostate cancer, surgery is the best option and the most common one. Radical prostatectomy involves complete removal of the prostate. During the surgery, a sample of the lymph nodes near the prostate is removed to determine whether the cancer has spread beyond the prostate gland. Because the seminal vesicles (the gland where the sperm is made) are removed along with the prostate, infertility is a side effect of this type of surgery. In order to minimize the risk of impotence (inability to have an erection) and incontinence (inability to control urine flow), a procedure known as "nerve-sparing" prostatectomy is used.

In a different surgical method, known as the transurethral resection procedure or TURP, only the cancerous portion of the prostate is removed, by using a small wire loop that is introduced into the prostate through the urethra. This technique is most often used in men who cannot have a radical prostatectomy due to age or other illness, and it is rarely recommended.

Radiation therapy involves the use of high-energy x rays to kill cancer cells or to shrink tumors. It can be used instead of surgery for early stage cancer. The radiation can either be administered from a machine outside the body (external beam radiation), or small radioactive pellets can be implanted in the prostate gland in the area surrounding the tumor.

Hormone therapy is commonly used when the cancer is in an advanced stage and has spread to other parts of the body. Prostate cells need the male hormone testosterone to grow. Decreasing the levels of this hormone, or inhibiting its activity, will cause the cancer to shrink. Hormone levels can be decreased in several ways. Orchiectomy is a surgical procedure that involves complete removal of the testicles, leading to a decrease in the levels of testosterone. Alternatively, drugs (such as LHRH agonists or anti-androgens) that bind to the male hormone testosterone and block its activity can be given. Another method tricks the body by administering the female hormone estrogen. When this is given, the body senses the presence of a sex hormone and stops making the male hormone testosterone. However, there are some unpleasant side effects to hormone therapy. Men may have "hot flashes", enlargement and tenderness of the breasts, or impotence and loss of sexual desire, as well as blood clots, heart attacks, and strokes, depending on the dose of estrogen.

Chemotherapy

Chemotherapy is the use of drugs to kill cancer cells. The drugs can either be taken as a pill or injected into the body through a needle that is inserted into a blood vessel. This type of treatment is called systemic treatment, because the drug enters the blood stream, travels through the whole body, and kills the cancer cells that are outside the prostate. Chemotherapy is sometimes used to treat prostate cancer that has recurred after other treatment. Research is ongoing to find more drugs that are effective for the treatment of prostate cancer.

Watchful waiting means no immediate treatment is recommended, but doctors keep the patient under careful observation. This option is generally used in older patients when the tumor is not very aggressive and the patients have other, more life-threatening, illnesses. Prostate cancer in older men tends to be slow-growing. Therefore, the risk of the patient dying from prostate cancer, rather than from other causes, is relatively small.

Prognosis

According to the American Cancer Society, the survival rate for all stages of prostate cancer combined has increased from 50% to 87% over the last 30 years. Due to early detection and better screening methods, nearly 60% of the tumors are diagnosed while they are still confined to the prostate gland. The five-year survival rate for early stage cancers is almost 99%. Sixty three percent of the patients survive 10 years, and 51% survive 15 years after initial diagnosis.

Prevention

Because the cause of the cancer is not known, there is no definite way to prevent prostate cancer. However, the American Cancer Society (ACS) recommends that all men over age 40 have an annual rectal exam and that men have an annual PSA test beginning at age 50. African-American men and men with a family history of prostate cancer, who have a higher than average risk, should begin annual PSA testing even earlier, starting at age 45.

A low fat diet may slow the progression of prostate cancer. Hence, the American Cancer Society recommends a diet rich in fruits, vegetables and dietary fiber, and low in red meat and saturated fats, in order to reduce the risk of prostate cancer.

Key Terms

Anti-androgen drugs

Drugs that block the activity of the male hormone.

Benign

A term for a tumor that does not spread and is not life-threatening.

Benign prostatic hyperplasia (BPH)

A noncancerous condition of the prostate that causes growth of the prostate tissue, thus enlarging the prostate and obstructing urination.

Biopsy

The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy

Treatment of the cancer with synthetic drugs that destroy the tumor either by inhibiting the growth of the cancerous cells or by killing the cancer cells.

Estrogen

A female sex hormone.

Hormone therapy

Treatment for prostate cancer, that involves reducing the levels of the male hormone testosterone, so that the growth of the prostate cancer cells is inhibited.

Lymph nodes

Small bean-shaped structures that are scattered along the lymphatic vessels. These nodes serve as filters and retain any bacteria or cancer cells that are travelling through the system.

Malignant

A tumor that is capable of spreading to other organs and poses a serious threat to a person's life.

Prostatectomy

The surgical removal of the prostate gland.

Radiation therapy

Treatment using high energy radiation from X-ray machines, cobalt, radium, or other sources.

Rectum

The last 5-6 inches of the intestine that leads to the anus.

Semen

A whitish, opaque fluid released at ejaculation.

Seminal vesicles

The pouches above the prostate that store semen.

Testicles

Two egg-shaped glands that produce sperm and sex hormones.

Testosterone

A male sex hormone produced mainly by the testicles.

Trans-rectal ultrasound

A procedure where a probe is placed in the rectum. High-frequency sound waves that cannot be heard by humans are sent out from the probe and reflected by the prostate. These sound waves produce a pattern of echoes which are then used by the computer to create sonograms or pictures of areas inside the body.

Further Reading

For Your Information

Books

• Dollinger, Malin. Everyone's Guide to Cancer Therapy. Somerville House Books Limited, 1994.
• Morra, Marion E. Choices. New York: Avon Books, 1994.
• Wallner, Kent. Prostate Cancer : A Non-Surgical Perspective. Seattle, WA: SmartMedicine Press, 1996.

  Organizations

• American Cancer Society. 1599 Clifton Road NE, Atlanta, Georgia 30329. (800) 227-2345.
• American Urologic Association. 1120 N. Charles Street, Baltimore, MD 21201. (410) 223-4310.
• Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623.
• National Institutes of Health. National Cancer Institute. 9000 Rockville Pike, Bethesda, MD 20892. (800)-422-6237.
• National Institute on Aging Information Center. (800) 222-2225.
• National Prostate Cancer Coalition. 1300 19th Street NW, Suite 400, Washington DC 20036. (202) 842-3600 ext. 214.

Gale Encyclopedia of Medicine. Gale Research, 1999.